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Northern Hawk Owl - Surnia ulula
Species of Concern Native Species Global Rank :
G5
State Rank :
S3
(see State Rank Reason below)
Agency Status USFWS :
MBTA
USFS :
BLM :
FWP SWAP :
SGCN3, SGIN
PIF :
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Copyright by Borror Laboratory of Bioacoustics, Department of Evolution, Ecology, and Organismal Biology, Ohio State University, Columbus, OH, all rights reserved.
State Rank Reason (see State Rank above)
Species has a small population and limited distribution in Montana.
Details on Status Ranking and Review
Northern Hawk Owl (Surnia ulula ) Conservation Status Review
Population Size
Score B - 50-250 individuals
Comment Approximately 30 nests have been documented and 54 owls have been banded in Montana between 1994 and 2011 (Owl Research Institute 2011). Thirteen breeding pairs documented in a combination of 2006 and 2007, most on the west side of Glacier National Park. This reasonably puts them in the population category of 50 to 250 individuals.
Range Extent
Score D - 1,000-5,000 km squared (about 400-2,000 square miles)
Comment 3,851 square kilometers based on Natural Heritage Program range maps that appear on the Montana Field Guide.
Area of Occupancy
Score U - Unknown
Comment Unknown.
Long-term Trend
Score E - Relatively Stable (±25% change)
Comment While much remains to be learned of the natural history of the species and their population status is poorly understood due to fluctuations corresponding to prey availability, there is no evidence the species is at risk and populations are likely to have been stable over the past 100 years. There are an estimated 10,000-50,000 pairs in North America. Wetlands in forest habitats are preferred habitat and are probably relatively stable since European arrival.
Short-term Trend
Score E - Stable. Population, range, area occupied, and/or number or condition of occurrences unchanged or remaining within ±10% fluctuation
Comment Breeding is regularly reported within the limited area in which the species is found on the west side of Glacier National Park. Populations are probably best regarded as stable over the short-term.
Threats
Score G - Slightly threatened. Threats, while recognizable, are of low severity, or affecting only a small portion of the population or area.
Comment Fire suppression has likely reduced hunting and prey habitat. Salvage timber harvest that removes potential nest snags represents a threat to the species. Timber harvest practices that provide more edge and more nest and perch trees would benefit the species. Shooting, trapping, vehicle collisions, pesticides, and transmission line electrocutions are probably more minor threats to the species.
Severity Low - Low but nontrivial reduction of species population or reversible degradation or reduction of habitat in area affected, with recovery expected in 10-50 years.
Comment As long as nest snags are retained species should respond to other disturbances quickly and it is likely that suitable nest snags would be retained in or adjacent to wetland habitats.
Scope Low - 5-20% of total population or area affected
Comment A high percentage of mature conifer forests are threatened by fire and there is some evidence that the species preferentially associates with post-burn forests.
Immediacy Moderate - Threat is likely to be operational within 2-5 years.
Comment Ongoing
Intrinsic Vulnerability
Score C - Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance; or species has high dispersal capability such that extirpated populations soon become reestablished through natural recolonization (unaided by humans).
Comment Not Intrinsically Vulnerable. Species matures quickly, reproduces frequently, and/or has a high fecundity such that populations recover quickly (< 5 years or 2 generations) from decreases in abundance. Species has good dispersal capabilities such that extirpated populations generally become reestablished through natural recolonization.
Environmental Specificity
Score C - Moderate. Generalist. Broad-scale or diverse (general) habitat(s) or other abiotic and/or biotic factors are used or required by the species but some key requirements are scarce in the generalized range of the species within the area of interest.
Comment Moderate Generalist. Broadly uses boreal conifer forests, usually dominated by spruce and fir, with the key limitation being nest sites and microtine rodent populations which are broadly distributed. The species is also believed to preferentially associate with post-burn forests for nest sites and foraging areas.
Raw Conservation Status Score
Score
3.5 - 0.75 (population size) – 0.25 (geographic distribution) + 0.0 (short-term trend) + 0.0 (threats) = 2.5
General Description
The Northern Hawk Owl is aptly named, as it more closely resembles an
Accipiter hawk species than an owl, both in morphology and behavior. This owl species is often quite visible, typically perching at the tops of trees. In flight, it moves at high speeds close to the ground or flaps its pointed wings using falcon-like strokes (Duncan and Duncan 2014).
The Northern Hawk Owl calls persistently during the breeding season. The display call of the male is a trilling, rolling whistling "
ululululululul " lasting up to 14 seconds, while the female's advertising call is shorter and less constant in pitch and rhythm, with a hoarser and shriller quality (Duncan and Duncan 2014).
For a comprehensive review of the conservation status, habitat use, and ecology of this and other Montana bird species, please see
Marks et al. 2016, Birds of Montana. Phenology
In Montana, observations for this species have been recorded every month of the year (Montana Bird Distribution Committee 2012). Nesting records as early as March with fledglings observed May-September (Montana Natural Heritage Program Point Observation Database 2014).
Diagnostic Characteristics
The Northern Hawk Owl is easily distinguishable from other species of owls by its long tail, prominent perching habit, and fast, maneuverable flight. The posture of the Northern Hawk Owl is more hawk-like than owl-like. The unique shape of this bird, including its moderately wedge-shaped tail, and overall coloration and appearance make it unlikely to be confused with any hawk species (Sibley 2014).
Species Range
Montana Range
Range Descriptions Western Hemisphere Range
Range Comments
Most breeding observations are in and around Glacier National Park (Montana Natural Heritage Program Point Observation Database 2014). Winter distribution covers all but the southeastern portion of Montana but is sporadic irruptive.
Observations in Montana Natural Heritage Program Database
Number of Observations: 169
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
SUMMER (Feb 16 - Dec 14)
Direct Evidence of Breeding
Indirect Evidence of Breeding
No Evidence of Breeding
WINTER (Dec 15 - Feb 15)
Regularly Observed
Not Regularly Observed
(Observations spanning multiple months or years are excluded from time charts)
Migration
Movement is sporadic, reflecting irregular movements of individuals in response to prey availability and climatic conditions (Duncan and Duncan 2014). In Montana, birds observed outside of known breeding area from August-February (Montana Natural Heritage Program Point Observation Database 2014).
Habitat
The Northern Hawk Owl breeds in moderately dense coniferous or mixed coniferous-deciduous forests often adjacent to wet meadows and marshes or open areas created by fire or logging (Duncan and Duncan 2014). This species needs suitable perching sites such as snags. Winter habitat similar to breeding habitat but may occur in more open areas depending on prey irruptions (Duncan and Duncan 2014).
Ecological Systems Associated with this Species
Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (common or occasional) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2012, Adams 2003, and Werner et al. 2004);
Evaluating structural characteristics and distribution of each ecological system relative to the species' range and habitat requirements;
Examining the observation records for each species in the state-wide point observation database associated with each ecological system;
Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of "observations versus availability of habitat".
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were listed as associated with an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not listed as associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system,
even if point observations were associated with that system.
Common versus occasional association with an ecological system was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species as represented in scientific literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignment of common versus occasional association.
If you have any questions or comments on species associations with ecological systems, please contact the Montana Natural Heritage Program's Senior Zoologist.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at:
mtnhp.org/requests ) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species' known geographic range.
Literature Cited
Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
Maxell, B.A. 2000. Management of Montana's amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
Commonly Associated with these Ecological SystemsForest and Woodland Systems
Grassland Systems
Recently Disturbed or Modified
Shrubland, Steppe and Savanna Systems
Wetland and Riparian Systems
Occasionally Associated with these Ecological SystemsRecently Disturbed or Modified
Food Habits
Studies conducted in other parts of the species' range revealed that the diet of the Northern Hawk Owl is dominated by voles (Duncan and Duncan 2014). The main Microtus species preyed upon in North America include Alaska vole (M. miurus ), Meadow Vole (M. pennsylvanicus ), Tundra Vole (M. oeconomus ), Long-tailed Vole (M. longicaudus ), and Yellow-cheeked Vole (M. xanthognathus ) (Duncan and Duncan 2014). Other small mammals and bird species that comprise the balance of their diet are numerous and may include shrews, moles, rabbits, hares, squirrels, mice, rats, lemmings, weasels, partridges, doves, woodpeckers, jays, robins, starlings, sparrows, buntings, blackbirds, grackles, and finches (Duncan and Duncan 2014).
Ecology
Ecological studies have yet to be conducted in the state. However, information from other areas of the species' range shows Northern Hawk Owls tend to occur in the greatest numbers in areas with temporarily high prey populations and may move long distances in response to changes in prey abundance. Population density generally is low (e.g., 4 pairs in 200 square kilometers in Norway; 1 pair per 500 square kilometer in Sweden) (Johnsgard 1988) with a maximum of 3 nests per 100 square kilometers in southwestern Yukon, Canada (Rohner et al. 1995). Home ranges in Europe ranged from 140 to 848 hectares, average 372 hectares (Baekken et al. 1987). In southern Alberta, they establish winter hunting territories (Johnsgard 1992).
Reproductive Characteristics
Limited breeding records exist for Montana. The first record of breeding in the western U.S. occurred in Montana in May of 1990, when a brood of 4 recently fledged young were observed in Polebridge. The first nest was confirmed when one was found in West Glacier in 1994 (eight young, seven fledged), and a second nest was recorded in 1995 when a female was photographed at a cavity site (Wright 1996, Montana Bird Distribution Committee 2012). Reproductive studies of Northern Hawk Owls in other areas of their range have found nesting to be in unlined hollows or cavities.
Management
No current management activities in Montana specific to Northern Hawk Owl are documented. Leaving residual trees in clear-cut logging areas can provide habitat for nesting and perching (Duncan and Duncan 2014).
Threats or Limiting Factors
Distribution and abundance of prey, particularly in winter, may be the greatest limiting factor to Northern Hawk Owl populations (Duncan and Duncan 2014).
References
Literature Cited AboveLegend:
Additional ReferencesLegend: Do you know of a citation we're missing? Surnia ulula ). Species Account Number 356. The Birds of North America Online (A. Poole, Ed.). Ithaca, NY: Cornell Laboratory of Ornithology; Retrieved 3/25/2008 from The Birds of North America Online databaseEffects of recreation on Rocky Mountain wildlife: a review for Montana . [Montana]: Montana Chapter of the Wildlife Society.
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